# What does orbital velocity look like near the ground

I'm looking for a video showing what it looks like to travel at 8k/s at a low altitude (ignoring air friction)?

All the orbital videos I've seen are so far from the ground that there's no real sense of speed. But i imagine a video shot from a plane flying quite low and then sped up to the right speed would be awesome. Even a computer rendering would be cool. Anyone ever seen or able to make such a thing?

• It'd look like a (very fast) fireball. ;) – Andrew Thompson Sep 10 '16 at 13:26
• Ignoring air friction, assuming 'quite low' to be ground level: The distance to the horizon is probably about 5km. At 8km/s you would have less than a second to see it. Add to that that the human mind often needs about one second to parse information. E.g. "hey, the traffic light went from red to green", or "hey, something appeared. Lets turn my head and focus my eyes. I would say you do not see anything or a blur. I do not have enough hard background to make this into an answer though. – Hennes Sep 10 '16 at 14:41
• If you watch a jet airliner pass by at cruising altitude, imagine it traveling about 30x faster (~600mph x 30 = 18,000mph ~orbital velocity). A jet might take a minute or two to pass from horizon to horizon (it's ~6 miles up so horizon will be quite far), so 30x faster means something on the order of a few seconds. A jet taking off is flying at maybe 170mph; that's about 1/100 orbital velocity. Imagine it passing overhead about 100x faster. – Anthony X Sep 10 '16 at 15:20
• Vis-viva equation sez: $v=\sqrt{GM_E/R_E}=\sqrt{3.98600x10^{14}/6371000}=7910$ m/s where $GM_E$ is Earth's standard gravitational parameter. At 30 frames per second, that's 264 meters or 870 feet per frame. Find a video of someone driving down the highway at 100kph on YouTube and throw out 284 out of every 285 frames and stitch it together. That sounds so fun I'm gonna try it tomorrow :) I think it would look better if it were at least a few hundred meters above the ground. – uhoh Sep 10 '16 at 15:41
• Well, let's say persistence of vision is 1/30 of a second. So I'll have to do a rolling (boxcar) average of the frames in order to see what it would "look like" visually. There are a several questions or answers here that involve issues related to the very fast ground speed. I think this is an interesting question to help bring that speed home! – uhoh Sep 10 '16 at 15:50

Nothing has ever travelled 8km/s in the Earth's lower atmosphere; and to be frank I'm not sure whether that's ever going to be possiblecitation needed.

As uhuh points out in the comments on your post, the velocity you need to orbit Earth at ground level is approximately 7910m/s, or a little over Mach 23.

I can however provide you video footage of something traveling at a little under half that, at a more leisurely pace of Mach 10: the Martin Marietta Sprint missile, which was introduced in 1972 as an anti-ballistic missile as part of the Sentinel Program.

By the time it reached its cruising speed in under 5 seconds, it had accelerated to a velocity of Mach 10 (or 3,430m/s), traveling somewhere between FL50 and FL1000.

There is video of it in action here.

The sheer amount of air friction generated required the use of an ablative heatshield which glowed white hot at over 3400°Csource, which you can see in the above video.

To travel 2.3x faster than this, you would need to have 5.3x the amount of kinetic energy; which would likely be highly unsurvivable even with the state of materials science today.

• Let me introduce you to the LHC :p – Antzi Sep 11 '16 at 5:40
• I did say ignoring air friction. I am looking for a visualization of the landscape going by. But very cool video nonetheless! – Innovine Sep 11 '16 at 5:42
• We've already seen well above 8km/sec--we even have one frame of film showing it. The cap from the Pascal-B nuclear test is estimated to have headed skyward at 66 km/sec--although it no doubt didn't make it all that far before vaporizing. – Loren Pechtel Sep 11 '16 at 23:29